These two decades have seen a surge in interest in the study of motivation throughout the field of language acquisition. Several distinguished motivational theories have been established: self-determination theory (Deci & Ryan, 1985), goal-setting theories (Locke & Latham, 1990), attribution theory (Weiner, 1992), self-worth theory (Covington, 1992) and self-efficacy theory (Bandura, 1993). In response to the negative trend that some learners lose interest in foreign language learning despite the best efforts by teachers, researchers have started to explore a different category of motivation, "demotivation". Dornyei (2001) defines a demotivated learner as "someone who was once motivated but has lost his or her commitment/interest for some reason" (p. 142). Demotivation has been researched in Japan, at primarily in the university and high school level. To overcome limitations of the previous studies, the current study explores the following three questions. (1) How do Japanese high school learners change their state of demotivation through? (2) How does each demotivator contribute to learners' demotivation? (3) When does demotivation start and what factors contribute to junior high school demotivation? The participants are 54 second year high school learners and 36 third year junior high students from a school in Japan. A 26 item-questionnaire and an in-house test were used to examine the high school learners. A 9 item-open ended questionnaire with two 5 Likert type questions was used to examine the high school learners. The data was analyzed qualitatively and quantitatively. High school learners' state of demotivation changed in the intensity toward "communicative method" and several variables are considered to contribute to demotivated learners. For junior high school learners, grammar and confidence issue are the stronger demotivator. Implications for practical classroom instructions, and recommendations for further research are given based on the results. (Contains 6 tables and 3 figures.)